An Aurora named STEVE???

09/04/18 11:33

A new “auroral” phenomena named STEVEby John Hlynialuk

A new type of auroral feature has been identified and it goes by the initials “S.T.E.V.E” standing for Strong Thermal Emission Velocity Enhancement. It has likely been around for a long time but only drew professional astronomers’ interest in July 2016. As it turned out I caught it on camera 4 years before that and 5 years before its nature was sorted out by satellite measurements in 2017.

Two years ago, a group of aurora photographers out west named the Alberta Aurora Chasers (avid imagers from all walks of life) came to the attention of a University of Calgary auroral scientist, Prof. Eric Donovan. The Aurora Chasers had been photographing aurora for years and occasionally imaged an unusual ray of purplish light that sometimes appeared along with normal aurora. It often showed up with multiple green “fingers” dubbed a “picket fence” nearby. The AAC member who showed such an image to Prof. Donovan thought he had captured a proton arc, but these features are sub-visual as the professor pointed out. Donovan had no idea what it was but he was intrigued and gave it the name “Steve” a whimsical label signifying something unknown (from an animated film where some animals name a forbidding hedge “Steve” to make it less ominous). Only later was the phenomena given the “backronym” STEVE as mentioned in the first paragraph.

Prof Donovan was able to get measurements of the gases in STEVE and detected a large increase in temperature and a westward velocity of the materials (the “T” and the “V” in STEVE’s official name). Undoubtedly, STEVE had been observed in the past but scientists did not have the all-sky cameras on the ground or satellites in orbit that could take Steve’s temperature and other vital signs. Neither had the community of amateur scientists (citizen scientists as they are now called) alerted professionals that there was something new in the heavens that needed explanation. Equally as important was the fact that cameras sensitive enough to easily photograph the faintest phenomena in the night sky had come into the hands of ordinary folks. A lot of them were trying them out taking pictures of star trails, the Milky Way, and also northern lights. A lot of factors came together, and as a result, STEVE’s time had come.

After I heard about STEVE, I went back and searched my own photo archives and found some images of what I called a “strange aurora” that appeared on Apr 25, 2012. Turns out it was STEVE! I was at the Fox Observatory and just closing up at 11:18 pm when I noticed this strange light in the sky. Thanks goodness I had my camera with me and before the display ended around midnight, I had taken about 5 dozen images. The image included here was made at 11:38 pm and showed the narrow purplish ray as well as the green picket fence feature that are characteristics of STEVE. That aurora was the second one in two weeks that I imaged from the ES Fox Observatory and there was no sign of STEVE on the previous occasion.

Canon 50D image with 10 mm WA lens (140° fov) at f/2.8, ISO 1250.

One of about 5 dozen images of an aurora that developed rather quickly on April 25 around 11:15 pm. It lasted less than an hour but during that time STEVE appeared in about half of the images. The narrow feature in purple above is the Strong Thermal Emission and Velocity Enhancement that gives STEVE its name.

The green “picket fence” features also accompany this new aurora type but may be a separate phenomena. There appear to be two rays, a prominent one near the horizon at centre and a fainter one that runs along the left edges of the pickets in centre giving an overall appearance of a large bird’s wing. A four-day old crescent Moon is just setting in the west behind the cloud bank and Procyon is the brightest star just above the horizon to the left of the clouds. STEVE is in front of Gemini with Castor and Pollux behind the some of the pickets just to the right of STEVE. The faint line crossing STEVE left to right is a contrail. See if you can pick out Leo (head down) just below the left centre of the image. Don’t let Mars throw you off since it was 5° to the east of Regulus on this date in 2012. Venus was also visible 13° to the right of the Moon but it has set in this image.

Further research is being done by Donovan’s aurora group. Interestingly enough, it turns out that although STEVE looks like an auroral ray, it is not actually an aurora per se. This also brings into question whether the picket fence features are not aurora as well, but that is still to be determined.